DST on Windows XP

We have over 200 XP systems on our network. About 26 or so reported that the patch issued by Microsoft did not change the time. We then went in to manually reset the time while we tried to figure out what may have went wrong with this handful of systems. An hour later the users reported the time switched back to the original time. Two questions: Anyone have any idea why the patch didn’t work on these systems, andtwo why does it change back. I’m sure the answer is the same for both, but just asking them separately. The systems were imaged so there SHOULDN’T be any difference. The users are just domain users – no special rights or permissions.